Epigenetic Alterations in Cryopreserved Human Spermatozoa: Suspected Potential Functional Defects

Area of Science:

• Reproductive biology
• Epigenetics
• Molecular biology

Background:

• Cryopreservation of human spermatozoa can induce micro-epigenetic alterations.
• Investigating these changes is crucial for evaluating cryopreservation effectiveness.

Purpose of the Study:

• To compare micro-epigenetic alternations in fresh versus cryopreserved human spermatozoa.
• To assess the impact of different cryopreservation protocols on sperm epigenetics.

Main Methods:

• Human spermatozoa were divided into fresh, vitrified (cryoprotectant-free), and conventionally frozen groups.
• RNA sequencing was performed on nine samples (three replicates per group) using Illumina technology.
• Gene set enrichment analysis (GSEA) and alternative splicing (AS) analysis were conducted.

Main Results:

• Vitrified spermatozoa showed enrichment in Gene Ontology (GO) terms related to mitochondrial function and male meiosis.
• Alternative splicing events, including exon skipping and retained introns, were identified in cryopreserved sperm.
• Cryopreservation can lead to epigenetic instability and altered mitochondrial activity.

Conclusions:

• Cryopreservation protocols can induce epigenetic instability in human spermatozoa.
• Changes include altered mitochondrial function and increased alternative splicing.
• Fresh spermatozoa are recommended for patients with cryopreservation-induced instability.